<span>Unidirectional flow in the heart is ensured because the heart contains valves that prevent backflow.
These valves keep the flow of the heart going in one direction (hence the name "unidirectional").</span>
Transcription is the process by which the DNA molecule makes an RNA molecule using enzyme RNA polymerase and other proteins. The mRNA is then used to generate proteins by a process called translation which occurs in the cytoplasm. Transcription occurs in the nucleus because DNA cannot leave the nucleus.
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by destroying or replacing native food sources.
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